<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>下拉内容菜单</title>
</head>
<body>

<h2>下拉内容的对齐方式</h2>
<p>left 和 right 属性指定了下拉内容是从左到右或从右到左。</p>

<div class="dropdown" style="float:left;">
    <button class="dropbtn">左</button>
    <div class="dropdown-content" style="left:0;">
        <a href="#">菜鸟教程 1</a>
        <a href="#">菜鸟教程 2</a>
        <a href="#">菜鸟教程 3</a>
    </div>
</div>

<div class="dropdown" style="float:right">
    <button class="dropbtn">右</button>
    <div class="dropdown-content">
        <a href="#">菜鸟教程 1</a>
        <a href="#">菜鸟教程 2</a>
        <a href="#">菜鸟教程 3</a>
    </div>
</div>
<style>
    .dropdown{
        display: inline-block;
        position: relative;
    }
    .dropdown-content{
        display: none;
        position: absolute;
        right: 0;
        min-width: 160px;
        box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);
    }
    .dropdown:hover .dropdown-content{
        display: block;
    }
    .dropdown-content a{
        display: block;
        padding:12px 16px;
    }
</style>
</body>
</html>
